Our research involves extracting 100 model structures for glycosylated and deglycosylated IgG1 from a large library of possible structures. These models produced calculated scattering curves that best fit the small angle X-ray and neutron data. Together, these best-fit models demonstrated conformational differences of the Fc region following glycan removal that accounted for changes in the scattering data. The ribbon cartoon images of the 16 IgG1 structures on the cover of the May 4 issue of Biophysical Journal were selected at random from the 100 and 100 best-fit structures for glycosylated and deglycosylated IgG1 and rendered in PyMOL. The image was stitched together and edited using Affinity Designer. We show just eight glycosylated best-fit structures and eight deglycosylated best fit structures.
In recent years, we have applied this methodology to the human antibodies IgA and IgG, along with the complement proteins Factor H and the Factor-H related protein 5. As a distinct structural technique, this provides a very different approach for solution structural determinations compared with other popular methods such as protein crystallography, cryo-electron microscopy, and nuclear magnetic resonance. The resulting structures are very informative when it comes to structure-function relationships because the analyses are performed at a molecular level.
Our combination of analytical ultracentrifugation, small angle X-ray, neutron scattering, and the atomistic modelling of these data sets has now been demonstrated to be powerful enough in probing more subtle structural changes such as glycan removal in antibodies. This methodology can be employed to other systems to probe small changes and larger structural events, such as unravelling the molecular structure of protein complexes.
To learn more about our research, visit https://www.ucl.ac.uk/biosciences/departments/structural-and-molecular-biology/smb-labs/structural-immunology-group-ucl.
- Valentina A. Spiteri, James Doutch, Robert P. Rambo, Jayesh Gor, Paul A. Dalby, Stephen J. Perkins